


The Cheap Trick Acceleration

by Liviapenn



Category: Big Bang Theory
Genre: Apocalypse, F/M, Nerdery, Road Trip, Sea World, Time Travel, Timeline Shenanigans, Yuletide 2009
Language: English
Status: Completed
Published: 2009-12-23
Updated: 2009-12-23
Packaged: 2017-10-05 02:34:57
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,381
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/36862
Author URL: https://archiveofourown.org/users/Liviapenn/pseuds/Liviapenn
Summary: <blockquote class="userstuff">
              <p>Penny racks her brain for the next twenty miles, trying to think of a subtle way to bring up the topic of meeting your time-traveling future self, or being sent on a mission to avert an apocalypse-related death. Finally she tells herself <i>Forget it, Penny, it's Nerdtown.</i> Sheldon and Leonard have weirder conversations six times a day. Sometimes before breakfast. Sometimes over Twitter.</p>
            </blockquote>





	The Cheap Trick Acceleration

**Author's Note:**

  * For [AylaPascal](https://archiveofourown.org/users/AylaPascal/gifts).



Penny is sleeping alone tonight. Leonard has some big polysyllabic project at work, so he won't get home till way late, and Penny has the morning shift tomorrow, which means she has to get up at like the butt crack of dawn. She's half-asleep when she hears someone stumbling around in her living room, and at first she smiles into her pillow because obviously Leonard finished early and decided to come crawl in with her. Then she glances over at her alarm clock and realizes that it's two in the morning, which Leonard knows is way too late to risk waking her when she's got to open. _Someone is in her living room_. Penny lies very still and listens. There's a funny humming sound and some clicking and then someone says "Oh, dear."

Penny grits her teeth, throws off her covers and grabs a Care Bear to pitch at Sheldon's head. This is not unreasonable. She's explained this to him before. If he knocks on her door before eleven AM he gets punched in the throat, and if he calls her a 'Morlockian wage slave' she randomizes everything in the fridge so that it's no longer organized to Sheldon's fridge organization system. And if he sneaks into her apartment in the middle of the night to organize her stuff, he gets whatever's close at hand chucked at him until he leaves again. (If she doesn't actually catch him doing it, she gets to go in _his_ room and inflict an amount of chaos commensurate to the order he's created in _her_ space. Sheldon had argued that he didn't accept that amendment to their friendship contract and without mutual agreement it was totally invalid, but Penny just started shredding up a post-it note while loudly humming the Spider-Man song, which she can't even believe she knows, and he shut up about it pretty fast.)

Penny leaps out of her bedroom like a ninja in Hello Kitty pajamas and pitches the Care Bear hard at the lean shape bending over her couch, and then she screams and recoils back and trips over her bathrobe and lands sort of half on her bed and slides off and hits the floor with a spine-rattling bump and screams again.

Half of her living room just-- _isn't there_. There's a weird ripple that hurts her eyes to look at, and on the edges it's kind of silvery and crinkly, and on the other side there's a big white and silver laboratory, with equations on whiteboards and big silver things wired up to big white things, and a lot of monitors scrolling numbers, and the whole thing is glowing and pulsing with a weird cold light. It's deadly silent, which is the weirdest part-- and also there's a shadowy shape like something out of the X-Files stepping out of _there_ and into _here_.

She just has time to think _I'm dreaming_ and then the strange lights in the living room go out. The lean shape moves closer, and Penny's arms and legs flail out of her control, backpedaling wildly. She manages to shove herself up to perch on the edge of her bed, and then the stranger who came through _whatever that was_ leans into her room, reaching inside for the lightswitch, and flicks it on.

"The Sheldon from the current timeline is going to burst in your front door very shortly," he says calmly. "Not as shortly as he would have if you and/or Leonard were in the habit of leaving the emergency key to your apartment in the bowl by the door, but still, with an alacrity that I feel does him a certain amount of credit-- if I do say so myself-- given that he would obviously be more than useless in a physical confrontation with an actual home invader or other miscreant."

It's Sheldon and it's not Sheldon. There have definitely been times that Penny has looked at Sheldon and seen exactly who he'd be in twenty or thirty years. Like, a crotchety, awkward guy in a horrible sweater and a grandpa windbreaker, rambling about stuff nobody cares about, right? Basically, exactly the same as he is now. So she _recognizes_ him, this Sheldon standing in her doorway in blue-gray corduroy pants and a thick green-gray sweater covered in darker gray and black squares. He's filled out a little, and his hairline is receding, but he's let it grow out some, and it's graying slightly at the temples. It's actually kind of a good look for him-- his frown lines look less petulant, more sort of dignified, and his eyes aren't quite as buggy now that his face is rounder.

_Holy crap on a cracker_, Penny thinks. As an actress and aspiring scriptwriter she feels like she should be more equipped than the average person to come up with some kind of witty quip. Certainly after all this time of knowing Leonard and Sheldon, she should be. She's probably witnessed more arguments about temporal paradoxes over the last three years than she's actually had hot, home-cooked meals. Still, sadly all she can come up with is "Wha, you, the... _You_...."

Sheldon-- the stranger, old Sheldon-- is still standing in the doorway. As he gave his little Sheldony speech about the bowl, Penny realizes, he was-- is-- knocking, very gently, on the door, first in the familiar three sets of three and then, as he started rambling, in further complicated patterns. Penny fixes her gaze on that bony wrist, the curled fingers, those robotically deliberate movements. She swallows hard.

"Hello, Penny."

Oddly enough, it's hearing his voice say her name that ultimately convinces her. "Oh my god, you are Sheldon."

"Very good," Sheldon says. "Occam's Razor would certainly seem to leave no other conclusion."

Out in the hall, Penny hears Sheldon and Leonard's door swing open.

"Penny!" someone shouts.

"I beg your pardon, but in order to avoid a possibly universe-ending temporal paradox," the older Sheldon says, stepping delicately over Penny's piled-up laundry, "I'm going to conceal myself in the bathroom. Also, I believe it's somewhat customary at this point for me to mention that the Sheldon native to this time period will soon appear, wearing a T-shirt silk-screened with Carmine Infantino's depiction of Barry Allen as the Flash. He will burst in your front door wielding Leonard's deluxe replica of the ThunderCats Sword of Omens, and of course his first words upon entrance will be Penny, Penny--"

"Penny!" Sheldon yelps again as he lets himself in. The older Sheldon slips into Penny's bathroom and closes the door just as the younger Sheldon appears in Penny's bedroom doorway, wielding a short, shiny sword with a big plastic jewel in the handle. He's wearing a red and yellow Flash tee.

Penny stares fixedly at him, not daring to look over her shoulder at the bathroom.

"Penny?" Sheldon lowers his deluxe replica sword. "Is everything all right?"

"Yes?" Penny says hopefully.

Sheldon blinks at her. "Did you fall out of bed?"

Penny looks down at her bare feet. "I guess?"

"I see... Were you having a nightmare?"

"Yes!" Penny is actually kind of impressed that Sheldon actually came up with a reasonably normal explanation for confusingly irrational human behavior. "I, a nightmare, me. Is what I had." She clears her throat and tries again. "I had a nightmare."

"Ah. Well, then..." Sheldon looks off to the left for a second, processing, then back at Penny. "There, there," he says, and offers her what is probably supposed to be a comforting smile.

"Oh, wow, yeah," Penny says, mostly because that seems like the quickest way to get him to stop. "I feel better now."

"Good," Sheldon says. The smile disappears. "There is, by the way, a solid scientific basis underlying the traditional recommendation of warm milk as a sleep aid. Would you like to hear it?"

"Hit me."

"Dairy products have a notably high tryptophan-to-protein ratio. Inside the body, tryptophan is converted to melatonin and serotonin, both of which aid in triggering a natural sleep response."

"Wow," Penny says, wondering if there's anything she could maybe do to trigger Sheldon's natural 'oh yeah I don't actually enjoy talking to people' response.

"Yes. Well. Good night, then," Sheldon says, and turns to go.

"Wait, wait!" Penny leaps to her feet, almost dying when she trips on some laundry. She grabs the doorframe for balance. "Which Flash is that?" she demands, pointing.

"What?" Sheldon glances downwards. "Barry Allen. Of course."

"And the artist is... Carlyle..." Penny squints.

"Carmine Infantino," Sheldon says. He's giving Penny a puzzled look, but it's only his usual 'gosh, people are weird' puzzlement and not, like, 'I seriously suspect that Penny is hiding something bizarre and potentially universe-destroying, what could it be,' type puzzlement.

"Right, of course. Carmine... right. Anyway, I'm fine now, so... you can go back to sleep. Thanks," Penny adds.

"Since there was no actual emergency, I didn't actually have the opportunity to do anything that would require your thanks, but I understand that social convention requires thanking me anyway. You're quite welcome," Sheldon says. "Good night, Penny."

"Good night!" Penny calls, shutting the door after him. She locks it and throws the bolt, which she hardly ever does-- who's going to walk up three flights of stairs to break her door down?-- and leans back against it.

When she glances back into her room, at the frosted glass of her bathroom door, her heart kicks it up another notch. _Please_ let it just be a weird, random dream that Sheldon happened to wake her up from. But she sees a dark shape through the glass, and the door opens, and Penny closes her eyes for a second and lets the door hold her up. _Not_ a dream. Wow.

"Thank you, Penny," Old Sheldon says. She stands still and watches as he comes out into the living room and starts messing around in her fridge. He checks the expiration date on a quart of milk, then frowns. "What's the date?"

"I know it's old, I just keep forgetting to grab it when I take the trash out," Penny says helplessly. "November twenty-third."

"That's genuinely horrifying." Old Sheldon puts the old milk back gingerly. "Although, I suppose, not quite as horrifying as actually arriving three months early, as that would have indicated serious flaws in either the design, construction or operation of the time machine."

"Crap on a _cracker_," Penny says, putting the heels of her hands to her temples and pressing in, hard.

"Surely you'd already come to the conclusion that my presence in this time period inarguably proves that my younger self will eventually discover a practical method of temporally displacing an individual?"

"Yes, Sheldon!" Penny yells. She can't believe she actually understood what he meant there. She's been hanging out with the guys way too long. The other week at work she actually called something 'incongruous' which is a word she only even knows because Sheldon said that something or other had a 'disturbing incongruity' to it and Penny had to look it up, because anything that disturbs Sheldon is a weapon she wants in her arsenal. Or wanted, anyway. She hushes as Sheldon glances quickly over her shoulder, in the direction of the hallway. He's got a point. The walls are so damn thin here. "What... why..." She crosses over to the couch, shoves some magazines onto the floor and flops back. "Oh god."

Older Sheldon rummages around in her kitchen. Penny hears the tink of a glass against the counter, the squeak of a bottle being opened-- is he _pouring her a drink?_ She sits up straight and stares.

"Thirty-five years from now," Sheldon says, pouring a generous double shot of tequila into one of Penny's drinking glasses, "someone will make me promise to, upon my arrival-- and I quote-- 'get some tequila down that poor girl ASAP.'"

He comes over to the couch and hands her the glass.

"Also I'm to tell you that there's some sort of malfunction in the meat freezer in the kitchen of the Cheesecake Factory and you won't be required to go to work tomorrow."

"Really?"

Sheldon nods.

"Here's to you, future Leonard," Penny says, raising her glass. "Good man." She knocks back the drink and takes a few deep breaths, feeling the heat spread down into her belly and out through her extremities. It helps settle her a little, and she looks back at Sheldon, a little more calmly. "Okay," she says. "So... do I have to stop Sheldon from taking the Enterprise to rendezvous with the fleet in the Laurentian system, or what?"

Sheldon snorts a breathy, hoarse laugh, then is immediately serious again. "Your intuitive grasp of the situation is impressive, if somewhat flippant... although I do appreciate, as always, the equation of myself with Spock. No, it's nothing so arduous. It's simply crucial that my younger self not go in to work tomorrow."

He pulls a slim piece of paper from his pocket and hands it to her. Penny takes it cautiously and unfolds it. It looks like a print-out of a Mapquest page, a thick purple line tracing down the California coast. She opens her mouth, about to object, but Sheldon (of course) talks over her.

"Tomorrow morning, after Leonard arrives home and goes to sleep, you will inform my younger self that you have recently been perusing the Internet for a suitable Christmas present to give Leonard. You will also tell him that you found a comic book collector in San Diego who offered to sell you a mint-condition, first-run copy of Young Marvelman #44 for forty-five dollars, and you will ask Sheldon if he believes that to be a fair price."

"Forty-five dollars for a comic book? What a rip-off!" Penny exclaims.

"Yes, I believe that would be the attitude most likely to cause him to demand to accompany you to San Diego in order to purchase said comic book." Sheldon says patiently.

"Wait, I have to drive Sheldon to _San Diego_ to keep him from going to work?" Penny whines. "Why can't I just lock him in his room, or slash Raj's tires? Why can't _you_ just go over there and tell Sheldon to stay home, or whatever it is he needs to know?"

"As I said before, universe-ending paradoxes would ensue," Sheldon says seriously.

"What!?"

"Universe-ending paradoxes," Sheldon repeats. Penny squints at him. "I know you've seen Star Trek, Penny. You attended at least one viewing during its first run in theaters, and I also recall your presence when Leonard and I watched both the DVD and Blu-Ray versions so that we could directly compare the visual and audio clarity of each. You quoted it not two minutes ago--"

"Yeah, but wasn't old Spock _lying_ to Kirk when he said that stuff about the paradoxes?"

Sheldon blinks.

"What?" Penny questions.

"I didn't think you were paying that close attention to the plot."

_"...Sheldon!"_

Sheldon tips his head to the side in a natural-looking 'Fair enough' kind of gesture. It's very weird to see Sheldon move like a normal person. Penny wonders if he's ever had sex, and then puts it out of her mind, _ew_, first because it's Sheldon, and second he's like totally old.

"Perhaps it's that you and my younger self have a cosmic, universe-changing destiny," Sheldon tells her. "Perhaps it requires you to personally experience the revelation of all that you could accomplish together, in order to develop a friendship that will define you both in ways you cannot yet realize."

Penny stares.

"Or not."

"I just," Penny begins, and Sheldon leans forward and looks right into her eyes, which startles her so much that she stops.

"Penny," he says, holding the look for a long, long moment. It's weird, because Sheldon almost never does that. Penny does it _to_ him, sometimes, gives him the death glare when he's being really annoying or bitchy, because it's kind of hilarious to see him freeze up like a rabbit in the headlights. And he always, _always_ breaks first. But this older, somewhat calmer Sheldon is matching her gaze, blue-gray eyes steady and accepting, and the moment is stretching on and on. Penny looks away, down into the bottom of her empty glass. "I understand that my younger self can be somewhat socially awkward, and that your relationship has been somewhat strained recently, due to the change in emotional dynamics between yourself and Leonard. But surely you understand the significance of my request. Do you think that I went to the effort of traveling back in time, defying many previously solid laws of physics, on a whim? Do you think I haven't worked out every detail of this mission, so as best to produce an optimum outcome? That includes selecting you as the best person to carry it out. I am entrusting you with a weighty responsibility, Penny. Do you accept it?"

"God, well, when you put it like _that_..."

"And afterward you can go to Sea World," Sheldon adds. "I know you like Sea World."

"I do like Sea World," Penny admits. It's been a long time since dinner, which was just a couple of microwave burritos anyway, and the tequila is starting to really hit her. She blinks heavily, swaying a little in her seat.

"Get some rest," Sheldon says, and he actually reaches out and claps her on the shoulder. It's incredibly weird. "I'll stop in later tomorrow night to assess your performance."

"Oh yay!" Penny says, and sits there, head spinning, as Sheldon lets himself out.

* * *

The next morning Penny wakes up on the couch with the taste of tequila in her mouth and the Mapquest page still crumpled in her hand, which is sad, because it means she can't pretend like it was all just a crazy dream. She goes over to Sheldon and Leonard's and everything works out the way future Sheldon said it would: Sheldon _insists_ that she go out to buy that comic book and _demands_ to come with her to make sure she's not getting ripped off by some unscrupulous scumbag who's going to take advantage of Penny just because she's a dumbass who doesn't know anything about comic books, no offense. (This is not what Sheldon is actually saying, but Penny is pretty good at translating by now.)

"None taken," she says, which is Penny-speak for "Don't worry, I'm not going to hit you," and steals one of Sheldon's English muffins. He stares at her and just shoves the whole plate over, and goes to make himself some new ones. And Leonard worries about them not getting along! Penny doesn't know what there is to worry about. Seriously.

* * *

Sheldon of course is full of opinions about which roads Penny should take and why Mapquest's trip planning algorithm sucks and blah blah blah. She listens and nods and totally ignores him. She's got a pounding headache and she's kicking herself for not asking Sheldon-- future Sheldon-- more questions last night. Why didn't she ask him what the future's like? Or if she ever makes it big as an actress? Why didn't she ask him who wins the Superbowl or the World Series or the World Cup next year? Oh, hell, Sheldon probably thinks the World Cup is a hippie coffee shop. God, why didn't she ask him if she and Leonard are still together in the future?

"Penny," Sheldon says, "I see that you have visited a mechanic."

"What?" Penny says.

"Your check engine light is no longer alight." Sheldon squints at her suspiciously. "I suppose it could have just burned out, due to extreme overuse the likes of which no check engine light could or should be expected to endure..."

"Why don't you just believe whatever makes you happy?" Penny suggests, tapping her hands on the steering wheel.

"That seems an extremely dysfunctional and inevitably disappointing way to go through life," Sheldon says.

"And yet it may be the only way you and I survive this road trip."

"Point well made," Sheldon acknowledges.

Penny drives in silence for a while.

* * *

Penny had kind of dreaded being stuck in the car with Sheldon, since he always seems to come up with some annoying road trip game or conversational gambit, but today he's being nice and quiet, spending most of his time staring blankly out the window or else scribbling in a notebook. After forty-five minutes or so she gets bored and actually asks him what he's working on. "As it turns out," Sheldon says, "long-wavelength cosmic background radiation--"

That keeps him going for fifteen minutes or so. Penny sighs. But she did ask.

Then somewhere along the way (Penny wasn't listening and missed the conversational segue) Sheldon starts talking about detecting and preventing earthquakes using science, and Penny nods along and that actually eventually becomes an interesting topic, or at least a topic Penny feels qualified to have an opinion about, which is Why People Like Disaster Movies. Sheldon chalks it up to immature logic modules in the brain just liking to see things get smashed, and on the whole Penny doesn't see much to argue with.

"I actually attended quite an interesting lecture last month," Sheldon goes on, "about the odds of long-term survival for the human race. The risk of a civilization-destroying disaster, natural or man-made, has been calculated by some to be as high as one percent per year. You and I, being relatively young specimens, are living in interesting times indeed, Penny. Although we certainly live quite comfortably compared to a stone age or medieval human, we have a higher chance of witnessing a true apocalypse than any other generation that has ever lived. Well, nearly any."

"Yay us," Penny says. She guns it and swerves around some asshole in the left lane who's been driving like a little old grandma lady for the last twenty miles.

"That's of course if we survive this road trip," Sheldon says tightly, bracing himself against the dashboard. Penny glares at him. He clears his throat and goes on. "Ironically enough, as Dr. Wells pointed out, when our current civilization eventually falls into ruins, the probability of long-term survival as a _species_ will rise quite dramatically, simply because so many major hazards will no longer exist."

Penny makes a face. The whole idea gives her the shivers. Obviously everything has a beginning and an end, but she doesn't like to think about that last thousand or so people who will ever exist, then the last twenty, then the last five... where will they even be living? In bombed-out ruins? In huts or cabins? Would they know they were the last people ever? Would they even remember what happened, why the glaciers melted or whatever? Super creepy.

"Is this like the hadron kaleidoscope thing?" she asks. "That doesn't help, does it? I mean with the odds that we're all going to blow ourselves up?"

"The only people who are apprehensive about the workings of the Large Hadron _Collider_ are those people with a sadly incomplete or faulty understanding of how it works." Sheldon rolls his eyes. "The whole thing is a perfect example of the media misunderstanding the fundamental principles of a scientific process and creating a worldwide controversy regarding a topic most laypeople don't have the slightest possibility of successfully comprehending. Why, Barry Kripke is back at the university at this very moment, working on a very similar-- though much smaller-scale, of course-- experiment, trying to determine the origin of matter-antimatter asymmetry. It is probably coming online as we speak. His entire experimental process is flawed, of course, and I highly doubt his tests will do anything to confirm his ridiculous theory, or indeed to produce any useful data whatsoever, but you don't see the media spinning it into some sort of terrible, supervillainous threat."

"He's not actually going to blow up the world, is he?"

"I don't even think he's going to blow up Pasadena. And even if I did, I would not hypothesize about it to the media. That sort of thing is extremely irresponsible, not to mention detrimental to the reputation of the sciences in the popular imagination."

"Oh, sure," Penny says. She stares out at the road ahead. Someone honks at her. "Shut up!" she yells, pulling back into the middle of her lane.

It occurs to her that the older Sheldon never actually told her _why_ it was so important that Sheldon didn't go to work today.

And it wasn't just that Sheldon couldn't go to work. Sheldon had to get out of town. Older Sheldon even bribed her with Sea World! This is clearly incredibly crucial.

But this-- this thing with Kripke-- it's got to be a coincidence, right? Right? Sure, Penny tells herself. Future Sheldon came back in time and sent her on a super important mission to get Sheldon out of town at the same time that Sheldon's annoying asshole co-worker is running an experiment that some people (stupid people, in Sheldon's opinion, but Sheldon's _not infallible_, and no one knows that better than Penny) believe might possibly blow up the world, and/or Pasadena?

Penny clutches the steering wheel tightly, squeezing hard and then letting go. No, she's being silly. It's just a coincidence.

But what if it's not?

Penny racks her brain for the next twenty miles, trying to think of a subtle way to bring up the topic of meeting your time-traveling self, or being sent on a mission to avert an apocalypse-related death. Finally she tells herself _Forget it, Penny, it's Nerdtown._ Sheldon and Leonard have weirder conversations six times a day. Sometimes before breakfast. Sometimes over Twitter. "Sheldon," she finally says, "is there a conceivable apocalyptic or post-apocalyptic scenario where for some weird reason Pasadena was going to blow up, and you could travel back in time to warn yourself that it was going to happen, so you could save one person, and you'd choose to let Leonard and Howard and Raj and everybody die, but save me? Would that ever happen?"

She stares fiercely ahead at the freeway, and pointedly doesn't look at Sheldon, but he doesn't answer for so long that she actually gets a little freaked out. When she glances over, he's plastered himself up against the passenger side door like Penny's suddenly been transformed into a rabid raccoon or something.

"What?!" she demands for what feels like the nine thousandth time since moving in across the hall from him and Leonard.

Sheldon's mouth moves silently a couple of times before he actually manages to speak. "Was that question an attempt to signal your romantic and/or sexual availability?"

"What? Ew! God, no!"

"Then why would you even--" Sheldon's voice goes all high and pitchy with panic. "What _possible_ reason--"

"Forget it!" Penny yells as loudly as she possibly can. "Never mind! I officially withdraw the question!"

After about thirty more miles Penny shoots Sheldon a sharp glance and he tenses all up again.

"Wait a minute. Why would you think I was--" Penny narrows her eyes. "Are you saying that you think the only reason you'd save me over the others is because in a post-apocalyptic world you might get to _bone_ me?"

"I said no such thing!" Sheldon comes as close to yelling as he ever does, barring an actual real emergency like someone being in his room or touching his stuff or something. "Obviously it's just a given that in such a scenario, repopulating the earth is going to be a concern. But of course that's-- clearly my _primary_ concern is that in any small rag-tag band of post-apocalyptic survivors, a variety of skills and life experiences is generally considered optimum, and therefore, in any such group that includes me, well, it's certainly unfortunate, but it is true that Leonard, Howard and Raj would be redundant. Whereas you--" He frowns. "Well, even after the apocalypse I'll still need someone to kill spiders for me."

"Oh my god," Penny says. Her hands are tingling. She can't feel her face or her feet. This might be a problem, because she needs her feet to, like, work the brakes. "You totally want to bone me."

"I do not," Sheldon says, in the least convincing lie he has ever spoken. "I absolutely do not--" He stops. It's like he can actually hear himself. Then he just sighs, long and ragged. It's kind of the most heartbreaking thing Penny has ever heard.

She doesn't look at Sheldon. She pulls the car over to the side of the freeway, flicks the hazard lights on, crosses her arms on the steering wheel and buries her face against her arms.

Sheldon doesn't say anything for a long while, which helps. He's said enough. How incredibly creepy is it to find out that someone you thought was your friend has secretly been crushing on you for probably the entire time he's known you? It's just-- Leonard never _said_ much about it but Penny always _knew_ that he liked her and would totally be her boyfriend in a hot second given half a chance. It wasn't like a deathly secretive secret or anything. Why does Sheldon have to be such a freak? Why couldn't he have said something about this before she got together with Leonard--!

"Oh god, I did not just think that," Penny mumbles, banging her head on the upper curve of the steering wheel.

Sheldon doesn't ask her what she's talking about, thank god.

Penny does _not_ think about Sheldon like that. Just because he's ridiculously fun to get in an argument with, just because he's one of the few people Penny's ever met in her entire life that she can't just steamroll over, just because he's tall and has nice hands and pretty eyes, sometimes, in the right light-- he's _Sheldon_ for god's sake. He's obsessive and territorial and arrogant and he turns into a huge baby when he's sick. She absolutely does not like Sheldon _like that_. Okay, maybe if they were in a post-apocalyptic world and everybody else that she ever knew was dead, including Kurt-- But probably still no.

Cars whiz by outside. Penny does not _actually_ wish one of them would veer onto the shoulder and hit her car and explode in a giant all-consuming fireball, but it's close.

Wait, she thinks.

Fireball.

What future Sheldon said...

"Sheldon," she says, lifting her head and looking Sheldon in the eyes, "I'm going to ask you a question and I want you to answer honestly."

"That seems fair," Sheldon says. As usual, he breaks eye contact first, glancing out the window.

"When you got in the car with me today," Penny pushes on, "what were the chances that we'd eventually start talking about apocalypses?"

"Near one hundred percent," Sheldon answers, confused but willing. "I've been eager to discuss the topic of the lecture for some time now, but since Leonard has been off his usual schedule I haven't been able to bring it up with him, and Raj finds the subject so existentially depressing it actually affects his productivity. I thought, being less sensitive, you'd--" Sheldon stops, and twitches in what looks like it's supposed to be a shrug. "I find that it does help me to talk these things out, even with... someone who lacks a physics background."

"Huh," Penny says. So maybe Pasadena isn't going to blow up after all, because it wouldn't be a very good plan if Penny caught on in the first hour or so and could still call and warn people, right? It's nice that Pasadena isn't going to blow up, because it's where all her stuff is. But this also means that maybe, terrifyingly, future Sheldon was actually telling the truth the _first_ time Penny asked why they had to go on this road trip, which she should have known anyway, because Sheldon can't fucking _lie_. "Oh my god."

"What?"

"We _do_ have a cosmic, universe-changing destiny that requires us to personally experience the revelation of all that we could accomplish together, in order to develop a friendship that will define us both in ways we cannot yet realize!" Penny blurts out. "Shit!" She looks over at Sheldon, guiltily.

"Oh my god," Sheldon says, stunned, fifty percent pure shock and fifty percent east Texas. "My theory of temporal displacement really _is_ practical as a means of enabling an individual to physically time travel!"

"No!" Penny says, but it's too late, Sheldon's on to her.

"You've met my future self! Haven't you? You _have!"_ Sheldon stares at her. "What was he like? Did he have a Nobel?"

"I don't know! He wasn't _wearing_ it!" Penny kind of hates that she knows that a Nobel is something you can wear. She really needs to get a life.

"Penny, think! What was he like?" Sheldon demands. "Did he look as though he had completed the Vulcan discipline of Kolinahr?"

Penny gives Sheldon the most stunningly oh-my-god-you-are-ridiculous look she has ever given him. Ever.

"It's a series of rituals through which--"

"I know what Kolinahr is, Sheldon!" Penny yells, then closes her eyes and slumps back in her seat and pretends to be dead, because that is seriously the only reasonable response to this day. "I can't believe I just said that."

"I can't either," Sheldon says. He sounds odd. Penny cracks her eyes open. Sheldon is giving her a weird look. She tries to imagine Spock giving someone that look. She can't quite manage it.

"Stop it," she says, very seriously.

Sheldon is still looking at her strangely. "Is this the sort of thing you can make someone stop by saying 'Stop it?'"

"Yes! It is!" Penny yells, hoping that yelling will make it true. "Now stop it!"

Maybe it does, because Sheldon blinks and looks away.

"Is there really a copy of Young Marvelman #44 on sale for forty-five dollars in San Diego?" he asks after a while.

"No," Penny says. "We'll get there and someone will tell us it got sold. I assume that was pre-arranged by your future self."

"Sheldon Prime," Sheldon corrects.

"Yeah, I won't call him that."

"Then," Sheldon says, and he actually sounds a little shaky, "can we just go home?"

"After we went to the comic book store I was going to console you with Sea World," Penny says apologetically.

"I do like Sea World," Sheldon reflects. "But I'd rather go home."

"Agreed," Penny says, and wearily flips the blinker over and pulls back onto the freeway. "I mean as long as you're sure Barry Kripke isn't going to end the world."

"I'm sure," Sheldon says. "...Ninety-nine percent sure."

Penny would demand clarification on this point, but the day so far has actually been so awkward that she kind of doesn't care if she gets blown up in a giant antimatter fireball, so at the next convenient exit she pulls off the freeway, turns the car around and starts back home.

* * *

"We can never, ever, _ever_ tell Leonard about this," Penny says, an hour or so later, as she pulls into a parking spot a block or two from their building. Getting out of the car, she takes a deep breath of dusty Pasadena air. Heaven.

"I assumed as much," Sheldon says, climbing out of his side of the car and stretching his arms up over his head. "The consequences for the timeline could be too devastating to contemplate."

"Well, actually," Penny says, too worn out even to raise her voice, "I meant the part where you like me and I'm Leonard's girlfriend and you're his roommate might be kind of awkward. But averting a temporal paradox is good too."

"Ah," Sheldon says. "Yes. I..." He stops dead in his tracks, trailing off as they pass the frozen yogurt shop on the corner, staring at someone inside. Penny stops and looks.

It's future Sheldon, sitting at the low counter against the window. He's actually wearing Sheldon's horrible brown grandpa jacket. He waves at Sheldon with his plastic spoon. After a second, Sheldon raises his hand in the Vulcan salute. Future Sheldon actually laughs, then sobers and raises his hand in a matching gesture.

Penny points at future Sheldon through the glass. "If you say 'Bazinga' I will kill you," she says loudly, mouthing the words exaggeratedly so that he'll be able to read her lips, if nothing else. "I know where he sleeps, you know that?" She jerks her thumb at Sheldon. "And if I kill him, you die! That's how it works!"

"I don't believe that's how it works," Sheldon says softly.

"Whatever, I may kill you anyway," Penny mutters.

"Understood. But right now, Penny, if you wouldn't mind..." Sheldon looks at her. She looks from him to his future self and back. Future Sheldon waits, patiently.

"Fine," she says, turning away to stagger the last few yards or so back to the apartment. "You two have fun. Ask him who wins the World Series for the next couple of years."

"Do you honestly think he knows who won the World Series _any_ year?" Sheldon drags his gaze away from his future self to give Penny an incredulous look.

"Point well made," Penny says.

"Thank you," Sheldon replies automatically. His voice is still very quiet. Penny moves closer, puts her hand on his back and gives him a shove towards the doors of the frozen yogurt shop. He stumbles and looks at her accusingly, but his hand is on the door now and there's nothing for him to do but push it open and go inside.

Penny turns around to go home. Maybe when she gets there she can go across the hall and Leonard will be poking around for a midnight snack or whatever it is when you're working graveyards, and he'll rub her shoulders or something. Maybe he'll want her to crawl in with him and they can snuggle. That'll be nice.

At least she knows that the world doesn't blow up for another twenty years or so. (At least she knows it _didn't_ in Future Sheldon's original timeline. That's how it works, right? She'll have to ask Sheldon.)

That's plenty of time to figure all this out.

* * *

_Traveling through established timelines is strictly forbidden. Except for cheap tricks. _  
\-- The Tenth Doctor, "Smith and Jones"


End file.
